绞盘设计技术手册（钢缆部分）

M[7N/MYX~3G+S0Performance of wire rope in a machine is affected by design of its sheaves and drums. Information about design of sheave and drum (diameter, the shape of the groove profiles and corresponding radius, the drum pitch and the fleet angle) is given in this article. Other useful technical information on wire ropes – measurement of diameter; generally accepted design factors; capacity of drums and reels; reserve strength; wire rope clips and wire rope end connections is also given in this article.

1T,YG/Nf0

Sheave and Drum Design

拓松汽车户外网 -:AC-dh+UF;K

Sheave and drum design factors affecting life / performance of a wire rope are as under.

MG_@:Ub0

Sheave and Drum Diameters

@U+npc.`0Rope breaking strength is determined in a standard test wherein fittings are attached to the ends of the rope and the rope is pulled in a straight line. If however, the rope passes over a curved surface (such as a sheave or pin) its strength is decreased. The amount of such reduction will depend on the severity of the bend as expressed by the D/d ratio where D is sheave / drum diameter and d is wire rope diameter. At smaller D/d ratios, the loss in strength increases quite rapidly.拓松汽车户外网 -#l SE.E&}J
i

3u`9H9dY0

ZD6Wab0

9f
gt5A!itk$HoS0The above graph shows strength efficiency of wire rope when bent over pins or sheaves of various sizes.拓松汽车户外网 -/q%z7H]};s'aN"E^

拓松汽车户外网 -\jf^{f$K
l"b v^

It can be seen that, a rope bent around a pin of its own diameter will have only 50% of the strength attributed to it in the standard test. This is called '50% efficiency'. Even at D/d ratios of 40, there may be a loss of up to 5%.

8A(qRz!S(w'b0拓松汽车户外网 -b0kr"M&U Q`YfR

In view of above, relevant standard or statutory requirement shall be followed. In absence of such requirements, the diameter of drum or sheave shall not be less than that given in the table below.

#ngs[T\a1J+jx4|0拓松汽车户外网 -p2m1~EY$Fl

拓松汽车户外网 -ib{8h dB,m:{~

Purpose

Construction

Minimum D/d Ratio

Colliery winding

6×6/1

90

6×12/6/1

70

Colliery haulage

6×6/1

70

Lifts and hoists

6×12/6/1

40

6×12/6+6F/1

40

6×9/9/1

50

8×12/6/1

32

8×9/9/1

40

General engineering applications

6×6/1

40

6×12/6/1

25

6×18/12/6/1

20

6×61

17

9AYG;S!z!P&_0拓松汽车户外网 -re$h;~?7_

Groove Dimensions

c]8S4H`&TY0It is necessary to have radius of the groove to be slightly larger than that of the rope passing over it.

T#p5j`N3Tc0拓松汽车户外网 -qWl
X$J%r-JFv

k%F#|*s'h"ul~0拓松汽车户外网 -Y$@R4xW:SGW};]

A too narrow groove will crush the rope and damage the wires soon. In too wide groove, the rope will wear more quickly at the point of contact and also cut a false groove in the pulley. In wide groove, the rope will not have lateral support and it will flatten under load. A rope shall be supported by the groove for one third of its circumference. Recommended groove dimensions for sheave and drum are as under.拓松汽车户外网 -_d$cK.KD#\7Kk)et

Groove Dimensions for a Sheave

拓松汽车户外网 -/FD)I1Qm!@

Recommended dimensions for radius, depth and throat angles are as under.拓松汽车户外网 -6@gwT6PUCl

Sheave and Drum Design as per IS 3177

拓松汽车户外网 -I:X)K(Tf
QP({

IS 3177 is a code of practice for electric overhead travelling cranes and gantry cranes other than steel works crane.拓松汽车户外网 -%h8em_ S

J?*e3y9J)w8Dk.s.Q7?g0The cranes are designed for four mechanism classes (Class 1 to 4) based on different duty factors (for strength and wear) and average life (running time per day and total life). For more information on various terms, please refer the specification.拓松汽车户外网 -tKnG%OK1s/e:Y

拓松汽车户外网 -BTE.W"[ O

Various dimensions as per the specification shall be as under.拓松汽车户外网 -D8^M x3~
[0^

D/d Ratio for Drums and Sheaves

/F&wN O&C4\+Z K0拓松汽车户外网 -XU$~2}/}6f,b

Rope Construction

D/d Ratio based on Mechanism Class

6×19

23 to 29

6×24, 6×36 and 6×37 group multi-strand

17 to 22

p?e?D!_!M0

@J+Lu+L S+|)j0

Radius of Groove in Drums and Sheaves

(Lp:q,p%]i gec?0拓松汽车户外网 -\4fc9@]F6^Pa

Diameter of Rope in mm

Increase over Rope Radius in mm

Up to and including 16

1.0

Over 16 and including 24

1.5

Over 24 and including 28

2.0

Over 28

3.0

拓松汽车户外网 - r/SCd;g[H

S;om*bRuG wR0

Grooving of Drums

^!mpE*R(H(|^0The contour at the bottom of the grooves shall be circular over an angle of approximately 120 degrees. The depth of the groove shall be not less than 0.35 times the diameter of the rope. The grooves of the drum shall be so pitched that there is, between adjacent turns of the rope, a clearance of not less than:拓松汽车户外网 -/Rm}8rT ~@gq;U/a

1.5 mm for ropes up to and including 12 mm diameter,

2.5 mm for ropes over 14 mm and including 8 mm diameter, and

3.0 mm for ropes over 28 mm diameter.

Grooving of Sheaves

0O7n!a.bldb-[VI C0Sheaves shall be grooved to a depth of not less than 1.5 times the diameter of the rope. The contour at the bottom of the grooves shall be circular over an angle of approximately 130 degrees.拓松汽车户外网 -G%xY+aj+\

Fleet Angle

拓松汽车户外网 -(TjVZ!P-|

Where a wire rope leads over a sheave and on to a drum, the rope will not remain in alignment with the sheave but will deviate to either side depending on the width of the drum and the distance from the fixed sheave.

;y6s-~5Bn%n4T"M'~0拓松汽车户外网 -.d3ktTK O1z

The fleet angle is the angle created at the point of intersection of a line drawn from the inside edge of the drum flange and along the centre line of the rope lead, and a line drawn from the centre of the drum at right angle to it. This angle is formed at the lead pulley. On a crane fitted with a grooved drum the angle should never exceed 4 degree and on a crane fitted with a flat-faced drum the angle should be between ½ degree and 2 degree maximum. If this angle is more, there will be heavy wear of the rope and groove sides.拓松汽车户外网 -6f1LRr \}(w!z

.M7lb;TBU1A0拓松汽车户外网 -:[6w,Y
IR5D0M

拓松汽车户外网 - \%^ys3t5Vp

To ensure the correct fleet angle, the following formula may be useful in finding the height of the lead pulley or the width of the drum, when one of these two measurements is known.拓松汽车户外网 -+]@?1|)Mi7Z0}

As per IS 3177, fleet angle shall not exceed 5 degrees.拓松汽车户外网 -a/y0wd&`uR

Diameter of a Wire Rope

拓松汽车户外网 -6C{3Vf+Up

拓松汽车户外网 -4P;X$Z.p-d/r*|f;{

拓松汽车户外网 -*|C#V9_uL7Ico

Diameter of a wire rope is the diameter of a circle circumscribing the strands. Care should be taken to see that it is measured correctly as shown above. The actual diameter usually varies from the nominal diameter of a rope. As per IS 2266, actual diameter can vary by -1% to 4 % of the nominal diameter of the rope.

0^3TwM[i2I$[,G%Z0拓松汽车户外网 -k"iV\kql#}

When measuring the rope diameter, don't measure the layer on the reel. Measure the rope when it is straight. To find the correct diameter at a point in a rope, the callipers must be placed over each pair of opposite strands, i.e. three separate readings for a six strand rope. The readings are then averaged.

G;c^!^6K0

n9p&z,S6P|k0The rope you are going to replace may be worn out and may measure less than the new rope. Measurement of rope to know its size shall be carried out where it is not worn out.

;} HL%vHU)fT&u0

Generally accepted design factors for various purposes (type of services)